Stark plug



C. G. ERNY SPARK PLUG Dec. 4, 1934.

Filed July 5, 1955 Patented Dec. 4, 1934 UNITED STATES PATENT OFFICESPARK PLUG Charles G. Emy, Philadelphia, Pa.

Application July 5, 1933, Serial No. 679,118

2 Claims. (01. 123-169) This invention relates to improvements in sparkplugs of the character disclosed in my copending application SerialNumber 659,883, and a principal object of the invention is to provide aspark plug of this character which shall be relatively simple of formand manufacture.

In the attached drawing:

Figure 1 is a side view of a plug made in accordance with my invention;

Fig. 2 is a sectional view of the plug, and

Fig. 3 is a fragmentary sectional view on the line 3--3, Fig. 1.

With reference to the drawing, the plug comprises a casing 1 open at oneend for reception of the insulator 2, and having at the opposite end areduced extension 3 which embraces the firing chamber 4. The insulator 2is held in place in the usual manner by a gland 5, and carries theterminal 6 which projects into the firing chamber in proximity to asecond terminal '7, one end of which is held in the side wall of thesaid extension and which extends transversely across the outer end ofthe firing chamber. The extension 3 is provided with screw threads 8 bymeans of which the plug may be mounted in the cylinder Walls of aninternal combustion engine in the usual manner, and these threads areterminated short of the outer end of the extension to provide anunthreaded portion 9 in which are formed the firing port or ports 10,these ports in the present instance being two in number and arranged atdiametrically opposite sides of the chamber. The outer end of thechamber is closed by the solid terminal wall 11 of the casing.

Extending diagonally through the wall of the extension from points atthe juncture of the threaded and unthreaded portions thereof is aplurality of ports 12 which enter the chamber 4 at a point adjacent theinner end of the chamber. It will be apparent that with thisconstruction the outer ends of the ports 12 are left open when the plugis installed in the internal combustion engine, and thereby aifordventilation for the inner end of the firing chamber.

The aforedescribed construction reduces the cost of manufacturing plugsof this character to a minimum and at the same time affords a highlyefficient device which is characterized by extreme ruggedness anddurability under the most exacting conditions, and in a materialreduction of carbon and other accretions in the interior of the firingchamber and on the exposed portions of the insulator 2. It will be notedthat by providing an unthreaded terminal portion of the extension 3 ofsufiicient length to permit the formation in the side walls thereof offiring ports of adequate size, it is possible to form these ports in asingle machining operation. By drilling the ports 12 from points at thejuncture of the threaded and unthreaded portions of the extension,advantage is taken of the shoulder at the outer terminal end of thethreads as a solid abutment for the drills in starting the operation. Inorder to provide a clearly defined shoulder at this point, it ispreferred to machine the unthreaded terminal end of. the extensionsubsequent to the formation of the screw threads 8.

The lower terminal 7 is inserted in position through a suitably formedopening in the wall of the firing chamber, and may subsequently bepermanently secured in position by a simple spotwelding operation. Sincethe inner end of this terminal element 7 is free, adjustment thereof toregulate the width of the spark gap may be readily accomplished byinsertion of a suitable tool through one of the firing ports 10 and by aflexure of the element 'I through the medium of said tool.

While the above described device involves the same principles andeffects the same advantageous results as the plug disclosed in myaforesaid pending application, the construction described above effectsa material economy in production and thereby constitutes a highlydesirable embodiment of my invention.

There may be minor modifications without departure from the invention.

I claim:

1. A spark plug comprising a hollow casing, an insulator in one end ofthe casing and forming the inner wall of a firing chamber located in theother end of the casing, screw threads on the exterior of the casingterminating short of the outer end of the firing chamber and forming atthe terminal end an undercut shoulder on the exterior of the casing, anda plurality of ports initiating in said shoulder and extending obliquelythrough the wall of the casing to the inner end of the firing chamber.

2. A spark plug comprising a hollow casing, an insulator in one end ofthe casing and forming the inner wall of a firing chamber located in theother end of the casing, and a shoulder on the outside of the wall ofsaid chamber intermediate the ends of the latter, said shouldercontaining the outer end of a port extending diagonally through the sidewall to the inner end of the chamber, and said wall having a second portin the outer end thereof communicating with the outer end of the firingchamber.

CHARLES G. ERNY.

